1. Field of the Invention
The present invention relates to a composition useful for producing a retardation film showing reversed wavelength dispersion of retardation. The present invention relates also to a film formed of the composition, and a polarizing plate and a liquid crystal display device comprising the film.
2. Related Art
Liquid crystal display devices have been used for more and more various purposes, as image display devices characterized by small power consumption and space saving. Previously, liquid crystal display devices have conventionally been seemed to have disadvantages due to their notable viewing-angle dependence of image. However, wide-viewing-angle liquid crystal modes such as a VA mode have been provided recently, and demand for liquid crystal display devices employing such a mode have increased more and more even in the market for requiring high-definition images such as the market for televisions. In accordance with the situation, the liquid crystal display devices are required to further improve their color quality, contrast, and also optical compensation performances of optical compensation components used for improving the viewing-angle dependence. For the purpose of improvement, there has been proposed an optical compensation component satisfying optical characteristics such that retardation in plane is smaller on the shorter wavelength side (reversed wavelength dispersion), and that retardation along thickness direction is larger on the shorter wavelength side (regular wavelength dispersion) (JPA No. 2005-242293).
The proposal relates to a method of producing a wide-band λ/4 plate (a polarizing plate converting linear polarization into circular polarization). This technique might be useful in that a single retardation film, which may function as a wide-band λ/4 plate alone, is obtainable, but retardation of the film falls within a narrow range, so that it has been necessary to stack a plurality of films in order to provide various optical characteristics by using the technique. Solving such a problem is required for providing not only a λ/4 plate but also other optical films.
Another problem of the high-viewing-angle liquid crystal mode such as VA mode resides in color shift, emerging in the black sate when the viewing direction is changed from the normal-line direction to the oblique direction inclined by a certain angle (viewing-angle direction).